1. Field of the Invention
The present invention relates to a method and apparatus for grinding the surface of a work which is made of a metal, a ceramic, a plastic or a composite material of some of these, and in particular to a method and apparatus for semi-finishing and polishing the surface of a work having a complicated irregular contour.
2. Description of the Prior Art
To adapt a dental prosthesis in the oral cavity of a patient for a long-term service, the configuration of the oral cavity of the patient has to be accurately reproduced and the dental prosthesis has to be precisely and smoothly finished. Since a dental prosthesis having a complex contour is produced by composting a metal, a ceramic and a resin, polishing the surface of the dental prosthesis is time consuming. For example, when a dental prosthesis is made of a metal and a ceramic, a typical process is as follows: at roughing steps, a mold material and an oxidized layer are removed using a roughest sandpaper, a sprue line is removed using a grinder, and the dental prosthesis is shaped using carborundum points, diamond points, carbide burs, a heatless stone and the like; and at semi-finishing steps, the dental prosthesis is polished using silicon points and sand, polished by a rotary brush loaded with an abrasive driven by a hand-held engine or lathe, and finally buffed as a mirror surface. When a dental prosthesis is made of a resin, unwanted parts such as burrs are cut using a stamp bar, the dental prosthesis is polished using paper corn or abrasive sand at a semi-finishing step, and then finally buffed. To complete the production of a dental prosthesis, a substantial time is consumed for grinding and polishing steps after molding. Throughout the above steps, particularly from semi-finishing to buffing, tips in a diversity of shapes including particulate shapes are available to adapt to a work of a prosthesis having a complex contour, and depending on the contour, these are selectively used to produce a smooth surface.
Since such a tip loaded on a high-speed lathe performs a spot polishing, time and energy are required to process uniformly the dental prosthesis on its overall area. Fine adjustment should be exercised in mounting the dental prosthesis and exertion of force on the tip. From the standpoint of environmental conditions, a great deal of abrasive powder, which is generated during the process, is likely to pose health problems to technicians who are exposed to such powder.
Not only in the above dental laboratory applications but in other applications, grinding and polishing processes are generally characterized by poor workability and poor working conditions, which remain to be solved.